Currently available breast cancer screening tools such as mammography and breast examination miss 10-40% of early breast cancers and require an invasive diagnostic biopsy to institute therapy. We propose a prospective multicenter trial including Ellis Fischel Cancer Center/University of Missouri, Stanford University and The Royal Marsden Cancer Center. The goal of the trial is to develop a highly predictive, noninvasive breast cancer early detection model using breast nipple aspirate fluid (NAF) and clinical information collected from women scheduled for breast surgery. Our hope is that this model will ultimately minimize the need for invasive diagnostic needle and surgical biopsies. In Phase I of the funding period, we will (1) standardize and optimize the collection of NAF at the three participating institutions, and (2) identify the panel of extracellular biomarkers from the NAF samples analyzed which provides the maximum sensitivity in breast cancer detection. The extracellular markers to be analyzed (prostate-specific antigen, basic fibroblast growth factor, gross cystic disease fluid protein-15, alpha-1 acid glycoprotein, urinary plasminogen activator (uPA), uPA inhibitor (PAI-1), and the Thomas-Friedrichson antigens TF and Tn) have each been measured in and associated with breast cancer in NAF. We propose Milestones which set forth specific criteria to allow us to determine our success in Phase I and assess if we can proceed to Phase II. In Phase II we will (1) use the panel of NAF biomarkers identified in Phase I, along with NAF cytology and clinical biomarkers linked to breast cancer risk, to develop a highly predictive breast cancer detection model, and (2) determine the best breast cancer detection model for various subsets of subjects, including pre- and postmenopausal women and those presenting with or without a palpable breast mass. [unreadable] [unreadable]